With modern developments in the motor vehicle industry, motor vehicle tires can no longer be considered as just as accessory to a motor vehicle, but are in fact an important design element in the vehicle. Satisfactory tire fitment is an imperative requirement from the point of view of safety and the handling qualities of the vehicle at the higher speeds which can be attained nowadays. However, in the production of motor vehicle tires, deviations from the desired tire shape which can have major effects on the handling characteristics and safety of the vehicle, are usually inevitable, due to the production procedures involved. Besides the conventional checking methods such as ascertaining unbalance and measuring radial and lateral run-out, checking tires in regard to uniformity in respect of their behaviour when subjected to various forces, and in regard to bead characteristic values, is becoming an aspect of increasing significance. In particular the bead contact pressure with which the tire is carried on the rim is as aspect of major significance. Particularly when a vehicle is travelling at high speeds or negotiating a curve, the tire is subjected to high forces which tend to pull it off the rim. If those forces overcome the resisting resilient forces of the tire and the air pressure therein, then the result is the feared rim-off effect which involves the tire jumping off the rim of the wheel. On the other hand the pressure forces with which the tire is carried on the wheel rim may not exceed certain values in order for the tire to be removable.
German patent specification No 1 773 367 discloses an apparatus for checking motor vehicle tires, in particular with a view to avoiding the rim-off effect referred to above. That apparatus involves clamping means which can be applied against the inside bead of the tire, being distributed around the periphery of a circle in relation thereto, and are displaceable in an outward direction. The apparatus further includes force measuring means which are associated with each of the clamping means, for measuring and recording, in relation to the respective angular position on the periphery of the tire, the compression forces with which the clamping means, in the form of clamping jaws, are pushed against the inside bead of the tire, covering the same distances in that operation. That makes it possible to arrive at an accurate picture of the bead characteristics.